Distributed System

CAP理论
一致性(Consistency)、可用性(Availability)、分区容错(Partition-tolerance)这三个特性不可兼得。
涉及到分布式系统取舍的权衡。

BASE
与ACID不同,分布式系统满足BASE原则:
- Basically Available:
- Soft state:
- Evenually consistent:

正向代理:客户端通过代理服务器请求服务端。客户端知道要请求的服务端,但是服务端不知道到底是哪个客户端发来的请求,比如某些科学上网工具。
反向代理:客户端直接向代理服务器发送请求。但是真正响应请求的是代理服务器后的服务端,反向代理服务器会帮我们把请求转发到真实的服务器那里去,反向代理隐藏了真实的服务端,比如我们访问www.baidu.com。
++两者的区别在于代理的对象不一样:正向代理代理的对象是客户端,反向代理代理的对象是服务端。++
Nginx就是性能非常好的反向代理服务器,用来做负载均衡。

http://www.cnblogs.com/hxsyl/p/4381980.html

Computers and computer networks are one of the most incredible inventions of the 20th century, having an ever-expanding role in our daily lives by enabling complex human activities in areas such as entertainment, education, and commerce. One of the most challenging problems in computer science for the 21st century is to improve the design of distributed systems where computing devices have to work together as a team to achieve common goals. In this book, I have tried to gently introduce the general reader to some of the most fundamental issues and classical results of computer science underlying the design of algorithms for distributed systems, so that the reader can get a feel of the nature of this exciting and fascinating field called distributed computing. The book will appeal to the educated layperson and requires no computer-related background. I strongly suspect that also most computer-knowledgeable readers will be able to learn something new. Gadi Taubenfeld is a professor and past dean of the School of Computer Science at the Interdisciplinary Center in Herzliya, Israel. He is an established authority in the area of concurrent and distributed computing and has published widely in leading journals and conferences. He authored the book Synchronization Algorithms and Concurrent Programming, published by Pearson Education. His primary research interests are in concurrent and distributed computing. Gadi was the head of the computer science division at Israel's Open University; member of technical staff at AT&T Bell Laboratories; consultant to AT&T Labs–Research; and a research scientist and lecturer at Yale University. Gadi served as the program committee chair of PODC 2013 and DISC 2008 and holds a Ph.D. in Computer Science from the Technion–Israel Institute of Technology.
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